Abstract P354: Pi3kg Signalling Is Crucial For Regulating The Cross Talk Between Cd8 T Lymphocytes And Vasculature In Hypertension

Abstract

CD8 effector T cells infiltrate target organs of hypertension (HTN). Phosphatidylinositol 3 kinase gamma (PI3Kγ) is a lipid kinase mainly distributed in immune and cardiovascular systems. In our previous work, we demonstrated a crucial role of PI3Kγ in blood pressure (BP) regulation. Here, we aim to identify signaling pathways involved in the acquisition of CD8 effectors functions in HTN. By taking advantage of a knock-in mouse model expressing a constitutively active PI3Kγ isoform (PI3Kγ CX/CX ), we tested the hypothesis that PI3Kγ regulates CD8 T cell trafficking in HTN. First, we found that PI3Kγ CX/CX mice were spontaneously hypertensive (SBP mmHg : PI3Kγ CX/CX : 131±1 vs WT: 108±0.5, p<0.001), displaying a significant activated CD8 T cells infiltration in perivascular spaces of kidneys (CD8+CD44+CD69 effector cells: PI3Kγ CX/CX : 7.6±2 vs WT: 1.95±0.2, p<0.001). To test a direct role of PI3Kγ in CD8 T cells, we purified these cells from PI3Kγ CX/CX spleens and performed an adoptive transfer of these cells in WT mice. Recipient mice increased BP and accumulated activated CD8 T cells in kidneys (SBP mmHg :CD8 CX/CX : 128±2 vs CD8 WT : 103±2, p<0.001). To test the interaction of CD8 T cells with vasculature, we co- cultured CD8 from PI3Kγ CX/CX mice with pressurized resistance arteries from WT mice for 3 days, finding that activated CD8 T cells significantly increased myogenic tone (an important regulator of BP) (%MT: CD8 CX/CX : 31±1; CD8 WT : 19±1, p<0.001). To deepen our hypothesis, we generated a conditional KO for PI3Kγ in CD8 T cells by crossing PI3Kγ flox mice with CD8a1cre-mice. We measured BP of PI3Kγ flox -CD8a1cre- mice observing that they were protected from BP increase upon Angiotensin II infusion by osmotic minipumps (SBP mmHg : PI3Kγ flox -CD8a1cre: 126±2 vs WT: 138±3, p<0.001).Then, we co- cultured CD8 T cells from PI3Kγ flox -CD8a1cre-mice with pressurized resistance arteries from WT mice, finding that CD8 T cells lacking PI3Kγ are unable to increased MT (%MT: PI3Kγ flox -CD8a1cre: 13±1 vs WT: 22±3, p<0.001). Taken together these data show that PI3Kγ signaling in CD8 T cells is crucial for priming of immune response in HTN.